1. Field of the Invention
The present invention relates to a surface roughness/contour shape measuring apparatus and, more particular to a surface roughness/contour shape measuring apparatus for measuring the surface roughness and contour shape of a three-dimensional workpiece along two axis directions without moving the workpiece.
2. Description of the Related Art
A surface roughness/contour shape measuring apparatus measures the surface roughness or contour shape of a workpiece by moving a pickup equipped with a stylus along the surface of the workpiece and by converting the amount of displacement of the stylus into an electrical signal which is read into a computer or the like for processing. FIG. 1 shows the basic configuration of a prior art surface roughness/contour shape measuring apparatus.
The surface roughness/contour shape measuring apparatus 1 is equipped with a probe (pickup) 6 for measuring the surface roughness of the workpiece placed on a table 2, and the pickup 6 is supported on a holder 5 fixed to a driving unit 4.
The pickup 6 has a stylus 7 at its tip, and the amount of displacement of the stylus 7 is converted into a voltage by a differential transducer (not shown) built into the pickup 6. This voltage value is converted by an A/D converter into a digital signal which is input to a data processing apparatus such as a computer (not shown). Thus, measurement data showing the surface roughness of the workpiece is acquired by the data processing apparatus.
As shown in FIG. 1, the driving unit 4 is fitted to a column 3 mounted vertically on the table 2 and, using a motor which is driven under instruction from the data processing apparatus, the driving unit 4 can move the holder 5 in the left/right direction (X direction) which is one predesignated direction parallel to the table surface on which the workpiece is placed; further, the driving unit 4 itself can be moved along the column 3 in the up/down direction (Z direction) perpendicular to the table surface according to the height of the workpiece.
In the prior art surface roughness/contour shape measuring apparatus 1, the direction in which the driving unit 4 can move the pickup 6 along the measurement surface of the workpiece has been limited to the X direction shown in the figure. This is because various standards (for example, JIS standard and ISO standard) defining the measurement of roughness only specify the roughness measured on a straight line.
Accordingly, in such (special) cases as the case of evaluating the surface roughness/contour shape in the X-Y plane, the measurement has been made by mounting on the table a Y-axis driving unit for moving the workpiece in the other one direction (Y direction) than the X direction on the table surface, in order to move the pickup 6 relative to the workpiece along the two in-plane directions (X and Y directions) parallel to the table surface.
Traditionally, such a three-dimensional surface roughness/contour shape measuring apparatus has been used exclusively, for example, for evaluating the luster of a painted surface or the surface property of a film or for measuring the flatness of a liquid crystal coated surface, and an important concern has been to provide a measuring apparatus having a wide measuring range and high versatility.